Archived 2016 topics: Silver-eared Mesia Leiothrix argentauris is being split: list Sumatran Mesia L. laurinae as Critically Endangered, and L. argentauris as Least Concern?

This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for passerines

Lynx Edicions and BirdLife International will soon publish the second volume of the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.

The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.

Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.

The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 2 of the checklist (for passerines) will begin to be incorporated into the 2016 Red List update, with the remainder to be incorporated into subsequent Red List updates.

Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.

Silver-eared Mesia Leiothrix argentauris is being split into L. argentauris and L. laurinae (including L. l. rookmakeri), following the application of criteria set out by Tobias et al. (2010).

Prior to the taxonomic change, Leiothrix argentauris (BirdLife species factsheet) was listed as Least Concern, on the basis that it did not approach the thresholds for listing as Vulnerable under any criteria. Although the population trend appeared to be decreasing, the decline was not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations).

Leiothrix laurinae was a relatively common member of montane forest habitat in Sumatra, being described one of the most frequently encountered birds on Gunung Kerinci prior to 2000. Subsequent to this there appears to have been a catastrophic collapse in the population with regular visits by birdwatchers to habitat in which it was common failing to record any since 2008 and extensive montane transect survey in 2013 not returning a single record (Eaton et al 2015). The pre-split species has long been a popular cage bird; large numbers were traded at the markets in Medan during 1997-2001 (Shepherd 2006) and recent trade volume was estimated at 184 birds per year based on monitoring in 2012-13 (Harris et al. 2015). Unfortunately the proportion of each taxon involved was not recorded during these market surveys such that it is now difficult to track any changes in the prevalence of L. laurinae in the trade. However, surveys on Java in 2014 and 2015 failed to record this species despite the presence of many other Sumatran highland species, while it was found in a market in Padang in October 2015 (Eaton et al. 2015). An expert review of the status of a set of Sumatran birds in 2014 considered that the species was ‘Severely Declining’, and it is also noted that localised forms are often preferred by buyers (Harris et al. 2015).

There appears to be a strong indication that this newly recognised species is in severe trouble, and that this is almost completely driven by the cage bird trade. As a desirable species in a region with high trapping pressure and several sympatric desirable (tradable) species, it is at risk of suffering continuing trapping below densities that would typically render exploitation uneconomically viable. There are still birds present, from the evidence of continued supply to the market and recent records from the Gunung Leuser Ecosystem protected area. However, the little data that exists indicates a very rapid decline across virtually the whole population over the past three generations (16.8 years: generation length for this species is set at 5.6 years). To have changed from being common and easily seen to being unrecorded over several months of transect survey in suitable habitat suggests a decline in excess of 80%, thereby qualifying the species as Critically Endangered under Criterion A2d+3d+4d. Should there be evidence that the decline is in the range of 50-79%, then the species would qualify as Endangered under Criterion A2d+3d+4d.

Comments and extra information to help assess the rate of this drastic population decline are sought.

References:

Eaton, J.A., Shepherd, C.R., Rheindt, F.E., Harris, J.B.C., van Balen, S. (B.), Wilcove, D.S. and Collar, N.J. 2015. Trade-driven extinctions and near-extinctions of avian taxa in Sundaic Indonesia. Forktail 31: 1-12.

Harris, J. B. C., Green, J. M. H., Prawiradilaga, D. M., Giam, X., Giyanto, Hikmatullah, D., Putra, C. A. and Wilcove, D. S. 2015. Using market data and expert opinion to identify overexploited species in the wild bird trade. Biol. Conserv. 187: 51–60.

Shepherd, C. R. 2006. The bird trade in Medan, North Sumatra: an overview. BirdingASIA 5: 16–24.

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3 Responses to Archived 2016 topics: Silver-eared Mesia Leiothrix argentauris is being split: list Sumatran Mesia L. laurinae as Critically Endangered, and L. argentauris as Least Concern?

  1. James Eaton says:

    There are still several sites in Aceh for rookmakeri of this species, though the sightings are infrequent and numbers small. Extensive surveys concentrating in Aceh are required to understand the current status in this area, as much of Gunung Leuser is difficult to access and highly remote, so good populations might still be found in this national park. I would be hesitant to uplist it higher than Endangered until further surveys have been conducted.

  2. Serene Chng says:

    TRAFFIC would like to share information on trade observations of this species, in a bid to quantify and better understand the threat from overexploitation.

    59 Leiothrix argentauris (laurinae) rookmakeri were observed from 9 stalls in three markets in Jakarta surveyed in July 2014 (Chng et al., 2015). Only one individual Leiothrix argentauris (laurinae) rookmakeri was recorded in an inventory of five markets in Surabaya, Malang and Yogyakarta in June 2015 (Chng and Eaton, 2016). A further five Leiothrix argentauris (laurinae) rookmakeri were also observed for sale in Bandung in September 2016.

    Unfortunately, although Leiothrix argentauris is listed on CITES Appendix II and there are international trade records for the species, information for subspecies level is unavailable and there is no way to differentiate the proportion of trade that is of L. argentauris and L. laurinae.

    Reference:
    Chng, S. C. L., Eaton, J. A., Krishnasamy, K., Shepherd, C. R. & Nijman, V. 2015. In the market for extinction: an inventory of Jakarta’s bird markets. TRAFFIC. Petaling Jaya, Selangor, Malaysia.

    Chng, S.C.L. & Eaton, J.A. 2016. In the Market for Extinction: eastern and central Java. TRAFFIC. Petaling Jaya, Selangor, Malaysia.

  3. Rob Martin (BirdLife International) says:

    On the basis that the population in the Gunung Leuser Ecosystem has not shown the rate of decline reported for more readily accessible montane forest in Sumatra, and held a large proportion of the global range of the species prior to the reported declines, the overall rate of decline is revised down from the above proposal. The apparent disappearance from montane forest throughout a large proportion of the range is still suspected to represent an acute decline in the population in excess of 50%.

    Preliminary proposals

    Based on available information, our preliminary proposal for the 2016 Red List would be to list Sumatran Mesia as Endangered under criterion A2d + A3d + A4d.

    There is now a period for further comments until the final deadline of 28 October, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from the initial proposal.

    The final 2016 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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